Liquid crystal displays are conventional plat plate displays at present; the thin film transistor liquid crystal displays (TFT-LCDs) are popular products among liquid crystal displays. A liquid crystal panel is an important component in a TFT-LCD, which generally comprises an array substrate and a color filter substrate which are assembled together, with a liquid crystal layer filled therebetween.
FIG. 1A is a schematic partial top structure view of an existing array substrate. FIG. 1B is a schematic side sectional structure view along line A-A in FIG. 1A. As shown in FIGS. 1A and 1B, this array substrate comprises a base substrate 1, on which data lines 5 and gate lines 2 which are cross each other are formed; the data lines 5 and the gate lines 2 define pixel units which are arranged in a matrix; each pixel unit comprises a TFT switch and a pixel electrode 11; the TFT switch comprises a gate electrode 3, a source electrode 7, a drain electrode 8 and an active layer 61; the gate electrode 3 is connected with a gate line 2, the source electrode 7 is connected with a data line 5, the drain electrode 8 is connected with the pixel electrode 11, and the active layer 61 is formed between the source and drain electrodes 7 and 8 and the gate electrode 3. The data lines 5, the gate lines 2, the gate electrodes 3, the source electrodes 7, the drain electrodes 8 and the active layer 61 of TFT switches, and the pixel electrodes 11 described above may be referred to collectively as conductive patterns. For the insulation between the conductive patterns, the conductive patterns provided in the same layer may be achieved by separate arrangement, and the conductive patterns provided in different layers may be achieved by providing an interlayer insulation layer sandwiched between the patterns. Additionally, the conductive patterns provided in different layers can be connected electrically with each other through via holes passing through the insulation layer between the layers.
During the display process of a TFT-LCD, the image signal voltages are input into pixel electrodes via data lines through TFT switches. Since it is necessary for the pixel electrodes to keep the image signal voltages in the period of one frame, a storage capacitor (Cs) is needed to be formed in each pixel unit to keep the image signal voltage on the pixel electrode. There are two ways to form the storage capacitor in the related art, one is form storage capacitors based on gate lines (Cs on Gate), the structure of which is shown in FIGS. 1A and 1B. The pixel electrode 11 in each pixel unit extends over the gate line 2 of the adjacent pixel unit, therefore this overlapped portions of the pixel electrode 11 and the adjacent gate line 2 form the storage capacitor.
The other way is to form storage capacitors based on common electrode lines (Cs on Common), the structure of which is as shown in FIGS. 2A and 2B. In this way, the array substrate further comprises common electrode lines 12 which are in the same layer as but not crossed with the gate lines 2, and the overlapped portions of the pixel electrode 11 and the common electrode line 12 form the storage capacitor. In the structure shown in FIGS. 2A and 2B, the difference compared with FIGS. 1A and 1B lies in the common electrode lines 12 and the ohmic contact layer 62 formed on the active layer 61 for reducing the contact resistance of the active layer 61 with both the source electrode 7 and the drain electrode 8.